In an IEEE 802.16 system, an automatic repeat request (ARQ) mechanism can be used on a per-connection basis to increase the probability that medium access control (MAC) layer service data units (SDUs) that are transferred over the wireless connection arrive at the receiver.
An ARQ transmitter has a state machine as described in IEEE 802.16 Section 6.3.4.6.2 with ARQ data blocks in one of four states: not sent, outstanding, discarded, and waiting-for-retransmission. An ARQ receiver also has a state machine. Synchronization of the transmitter and receiver ARQ state machines is governed in two manners. There is a transmitter ARQ sync loss timer managed by the transmitter state machine, and each instance where ARQ_TX_WINDOW_START is updated, the transmitter ARQ sync loss timer is reset. When the transmitter ARQ sync loss timer exceeds the value of ARQ_SYNC_LOSS_TIMEOUT, the transmitter state machine initiates a reset of the connection's state machines. Simultaneously, synchronization of the ARQ state machines is also governed by another timer managed by the receiver state machine. Each instance where ARQ_RX_WINDOW_START is updated, a receiver ARQ sync loss timer is reset. When the receiver ARQ sync loss timer exceeds the value of ARQ_SYNC_LOSS_TIMEOUT, the receiver state machine initiates a reset of the connection's state machines.
Thus, a reset of a connection's state machines can be triggered by either the transmitter or the receiver and is often triggered by both. During an ARQ reset, all transmitter SDUs with blocks in the discarded state are discarded, and all receiver SDUs that are incomplete are discarded. When, for any reason, there is no data available for an ARQ-enabled connection, the transmitter ARQ sync loss timer, the receiver ARQ sync loss timer, or both timers will expire and an ARQ reset will be performed. In this situation, the reset is superfluous exactly because there is no data available to transfer. Thus, there is an opportunity to avoid this superfluous reset.
Given that the maximum ARQ_SYNC_LOSS_TIMEOUT value is equivalent to 0.6 seconds, superfluous resets occur frequently when the ARQ connection is communicating using Hypertext Transfer Protocol (e.g., surfing the Internet). There are, of course, other situations where superfluous resets occur. The various aspects, features, and advantages of the disclosure will become more fully apparent to those having ordinary skill in the art upon careful consideration of the following Drawings and accompanying Detailed Description.